Creating and managing users and groups

Creating and managing users and groups is an essential aspect of system administration in CentOS. Here's how you can create and manage users and groups in CentOS:

1. Creating Users:

• To create a new user, you can use the useradd command followed by the username. For example:

  sudo useradd username 

  Replace username with the desired username.

• You can also specify additional options when creating a user, such as the user's home directory and login shell. For example:

  sudo useradd -m -s /bin/bash username 

  This command creates a user with a home directory and sets /bin/bash as the default login shell.

2. Setting User Password:

• After creating a user, you need to set a password for the user using the passwd command. For example:

  sudo passwd username 

  You will be prompted to enter and confirm the password for the user.

3. Creating Groups:

• To create a new group, you can use the groupadd command followed by the group name. For example:

  sudo groupadd groupname 

  Replace groupname with the desired group name.

4. Adding Users to Groups:

• To add a user to an existing group, you can use the usermod command with the -aG option. For example:

  sudo usermod -aG groupname username 

  Replace groupname with the name of the group and username with the name of the user you want to add to the group.

5. Listing Users and Groups:

• To list all users on the system, you can use the getent command with the passwd database. For example:

  getent passwd 

• To list all groups on the system, you can use the getent command with the group database. For example:

  getent group 

6. Modifying Users and Groups:

• You can modify user and group properties using commands like usermod and groupmod. For example:

  sudo usermod -s /bin/bash username 

  This command changes the login shell for the specified user.

• Similarly, you can use groupmod to modify group properties. For example:

  sudo groupmod -n newgroupname oldgroupname 

  This command renames an existing group.

7. Removing Users and Groups:

• To remove a user, you can use the userdel command. For example:

  sudo userdel username 

• To remove a group, you can use the groupdel command. For example:

  sudo groupdel groupname 

8. Additional User and Group Management Tools:

• CentOS also provides graphical tools like usermanager and groupmanager for managing users and groups in a desktop environment.